mtask.c

// mtask.c
#include "bootpack.h"

struct TASKCTL* taskctl;
struct TIMER* task_timer;

struct TASK* task_now(void)
{
  struct TASKLEVEL* tl = &taskctl->level[taskctl->now_lv];
  return tl->tasks[tl->now];
}

void task_add(struct TASK* task)
{
  struct TASKLEVEL* tl = &taskctl->level[task->level];
  tl->tasks[tl->running] = task;
  tl->running++;
  task->flags = 2;
  return;
}

void task_remove(struct TASK* task)
{
  int i;
  struct TASKLEVEL* tl = &taskctl->level[task->level];

  for (i = 0; i < tl->running; i++) {
    if (tl->tasks[i] == task)
      break;
  }

  tl->running--;
  if (i < tl->now) {
    tl->now--;
  }
  if (tl->now >= tl->running) {
    tl->now = 0;
  }
  task->flags = 1;

  for (; i < tl->running; i++) {
    tl->tasks[i] = tl->tasks[i + 1];
  }

  return;
}

void task_switchsub(void)
{
  int i;
  for (i = 0; i < MAX_TASKLEVELS; i++) {
    if (taskctl->level[i].running > 0)
      break;
  }
  taskctl->now_lv = i;
  taskctl->lv_change = 0;
  return;
}

void task_idle(void)
{
  for (;;) {
    io_hlt();
  }
}

struct TASK* task_init(struct MEMMAN* memman)
{
  int i;
  struct TASK *task, *idle;
  struct SEGMENT_DESCRIPTOR* gdt = (struct SEGMENT_DESCRIPTOR*)ADR_GDT;

  taskctl = (struct TASKCTL*)memman_alloc_4k(memman, sizeof(struct TASKCTL));
  for (i = 0; i < MAX_TASKS; i++) {
    taskctl->tasks0[i].flags = 0;
    taskctl->tasks0[i].sel = (TASK_GDT0 + i) * 8;
    taskctl->tasks0[i].tss.ldtr = (TASK_GDT0 + MAX_TASKS + i) * 8;
    set_segmdesc(gdt + TASK_GDT0 + i, 103, (int)&taskctl->tasks0[i].tss, AR_TSS32);
    set_segmdesc(gdt + TASK_GDT0 + MAX_TASKS + i, 15, (int)taskctl->tasks0[i].ldt, AR_LDT);
  }
  for (i = 0; i < MAX_TASKLEVELS; i++) {
    taskctl->level[i].running = 0;
    taskctl->level[i].now = 0;
  }

  task = task_alloc();
  task->flags = 2;
  task->priority = 2;
  task->level = 0;
  task_add(task);
  task_switchsub();
  load_tr(task->sel);
  task_timer = timer_alloc();
  timer_settime(task_timer, task->priority);

  idle = task_alloc();
  idle->tss.esp = memman_alloc_4k(memman, 64 * 1024) + 64 * 1024;
  idle->tss.eip = (int)&task_idle;
  idle->tss.es = 1 * 8;
  idle->tss.cs = 2 * 8;
  idle->tss.ss = 1 * 8;
  idle->tss.ds = 1 * 8;
  idle->tss.fs = 1 * 8;
  idle->tss.gs = 1 * 8;
  task_run(idle, MAX_TASKLEVELS - 1, 1);

  return task;
}

struct TASK* task_alloc(void)
{
  struct TASK* task;
  for (int i = 0; i < MAX_TASKS; i++) {
    if (taskctl->tasks0[i].flags == 0) {
      task = &taskctl->tasks0[i];
      task->flags = 1;
      task->tss.eflags = 0x00000202; // IF = 1
      task->tss.eax = 0;
      task->tss.ecx = 0;
      task->tss.edx = 0;
      task->tss.ebx = 0;
      task->tss.ebp = 0;
      task->tss.esi = 0;
      task->tss.edi = 0;
      task->tss.es = 0;
      task->tss.ds = 0;
      task->tss.fs = 0;
      task->tss.gs = 0;
      task->tss.iomap = 0x40000000;
      task->tss.ss0 = 0;
      return task;
    }
  }
  return 0;
}

void task_run(struct TASK* task, int level, int priority)
{
  if (level < 0) {
    level = task->level;
  }
  if (priority > 0) {
    task->priority = priority;
  }

  if (task->flags == 2 && task->level != level) {
    task_remove(task);
  }
  if (task->flags != 2) {
    task->level = level;
    task_add(task);
  }

  taskctl->lv_change = 1;
  return;
}

void task_sleep(struct TASK* task)
{
  struct TASK* now_task;
  if (task->flags == 2) {
    now_task = task_now();
    task_remove(task);
    if (task == now_task) {
      task_switchsub();
      now_task = task_now();
      farjmp(0, now_task->sel);
    }
  }
  return;
}

void task_switch(void)
{
  struct TASKLEVEL* tl = &taskctl->level[taskctl->now_lv];
  struct TASK *new_task, *now_task = tl->tasks[tl->now];
  tl->now++;
  if (tl->now == tl->running) {
    tl->now = 0;
  }
  if (taskctl->lv_change != 0) {
    task_switchsub();
    tl = &taskctl->level[taskctl->now_lv];
  }
  new_task = tl->tasks[tl->now];
  timer_settime(task_timer, new_task->priority);
  if (new_task != now_task) {
    farjmp(0, new_task->sel);
  }
  return;
}